Germs Study

We're looking into something that's supposed to help keep you healthy, but in some cases it may have a down-side, too: those sanitizers that are all over your supermarket and in drugstores.

it's possible, some experts believe, to be too clean.

our report from nbc news chief medical editor Dr. Nancy Snyderman.

Slather on sanitizer. Wipe down surfaces. Repeat.

It's become a familiar ritual in our battle against germs.

But the dirty little secret is that most germs are harmless and, in fact, many are GOOD for us.

Dr. Richard Gallo: "If you're in a normal environment and you're not exposed to germs, overuse of hand sanitizers might actually make you more susceptible to the next infection that comes along."

Dr. Samuel Friedlander says our super clean lifestyle could be partly to blame for the rise in the number of people with allergies and asthma.

Dr. Samuel Friedlander: "I view the immune system as an army and if the army doesn't have something to fight, in many cases, it will fight allergens."

Eight-year-old Olivia Osburn has allergies... so do three of her friends at school.

Recent studies give new weight to the decades-old "hygiene hypothesis"... that exposure to some germs helps our immune systems tell the difference between harmful and harmless irritants.

This summer, researchers found Amish children raised on farms in the U-S had dramatically fewer asthma and allergy problems. The findings follow a previous study in Europe that showed kids raised on cow farms had reduced risks of allergies.

Dr. Samuel Friedlander: "there is a link between the farming community having less allergies and those people with dogs in their households at birth and those kids having less allergies as they grow up."

Experts say alcohol-based sanitizers DO have an important place in our lives... in hospitals, in public places and for those who have compromised immune systems.

Dr. Samuel Friedlander: "the key is to balance personal hygiene and public safety // and weigh that against the risks of allergic diseases."